Low back pain affects coordination between the trunk segments but not variability during running.

This study aimed to analyze the coordination and variability between the thorax, lumbar, and pelvis segments in runners with chronic low back pain group (LBPG) and matched control group (CG). Twenty-six recreational runners were evaluated on a treadmill at 3.3 m/s. The coordination of the pelvis-lumbar and lumbar-thorax in all three planes and between the transverse and frontal plane of the lumbar segment were evaluated using the vector coding technique. Coordination was analyzed via histograms with the percentage of each pattern and the coupling angle during the cycle. The variability coordination was calculated from the angular deviation between the cycles. Differences were observed in the coordination patterns and in the coupling angle during the cycle. Between the pelvis-lumbar in the frontal plane, the LBPG (x¯ = 50.6% (SD = 10.7)) presented more in-phase pattern than the CG (38.6% (8.7; P = 0.05). For the lumbar-thorax, differences occurred in all planes. Between the frontal-transverse plane of the lumbar segment, the LBPG (27.6% (7.9)) presented more in-phase pattern than the CG (38.6% (8.7); P = 0.02). The variability did not demonstrate the differences between the groups; these differences were observed in coordination between the lumbar and adjacent segments in all planes. The model of rigid segments and the coordination analyses were sensitive to detect these differences, and the presence of more in-phase patterns could be related to the protection mechanism in order to avoid painful movements.